Anyway you answer helped me – thank you. The mistake was in defined of constants. In my class I have lots of constants (like this: #define xy 1234) and it´s caused the error. Now I´m (thank to you) a little bit smarter. How you wrote probably some constant was define twice…

If possible, you could change to true constants, instead of preprocessor macros.

If you need to stick to macros, it's always a good idea to start the macro names with some prefix common to you project, so for example instead of just using NUMFILES, it would be better to use QTC_NUMFILES (if we assume coding for Qt Creator here). This way you have much better chances that it doesn't clash with some other #defines.